U.S. patent application number 13/144106 was filed with the patent office on 2012-07-05 for black pigment dispersion.
This patent application is currently assigned to BASF SE. Invention is credited to Thomas Eichenberger, Margherita Fontana, Andreas Gernandt, Christoph Krebs, Bernd Lamatsch, Achim Lamatsch (Heir), Marian Lanz, Dario Perera, Frank Oliver Heinrich Pirrung, Thomas Ruch.
Application Number | 20120172498 13/144106 |
Document ID | / |
Family ID | 40911912 |
Filed Date | 2012-07-05 |
United States Patent
Application |
20120172498 |
Kind Code |
A1 |
Fontana; Margherita ; et
al. |
July 5, 2012 |
BLACK PIGMENT DISPERSION
Abstract
Described is a pigment dispersion which is useful for
electrophoretic displays comprising .alpha.) a
bis-oxodihydro-indolylene-benzodifuranone colorant of the Formula
(I) wherein the substituents are defined as in claim 1, .beta. a
specific polymeric dispersant, and .gamma.) a solvent which is
suitable for dispersions used in electrophoretic displays. Also
described are novel colourants and dispersants. ##STR00001##
Inventors: |
Fontana; Margherita;
(Thalwil, CH) ; Lanz; Marian; (Roschenz, CH)
; Pirrung; Frank Oliver Heinrich; (Grunstadt, DE)
; Gernandt; Andreas; (Ludwigshafen, DE) ; Perera;
Dario; (Basel, CH) ; Ruch; Thomas; (Delemont,
CH) ; Krebs; Christoph; (Pratteln, CH) ;
Eichenberger; Thomas; (Basel, CH) ; Lamatsch;
Bernd; (Riehen, CH) ; Lamatsch (Heir); Achim;
(Waldkirch, DE) |
Assignee: |
BASF SE
Ludwigshafen
DE
|
Family ID: |
40911912 |
Appl. No.: |
13/144106 |
Filed: |
January 7, 2010 |
PCT Filed: |
January 7, 2010 |
PCT NO: |
PCT/EP2010/050089 |
371 Date: |
November 16, 2011 |
Current U.S.
Class: |
524/94 ; 526/263;
548/456 |
Current CPC
Class: |
C07D 493/04 20130101;
C09B 57/00 20130101; C09D 17/003 20130101; G02B 5/223 20130101;
C09B 7/08 20130101 |
Class at
Publication: |
524/94 ; 548/456;
526/263 |
International
Class: |
C08K 5/3417 20060101
C08K005/3417; C08L 39/08 20060101 C08L039/08; C08F 226/08 20060101
C08F226/08; C07D 493/04 20060101 C07D493/04 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 19, 2009 |
EP |
09150843.2 |
Claims
1. A dispersion which is useful for electrophoretic displays
comprising .alpha.) a bis-oxodihydro-indolylene-benzodifuranone
colorant of the formula I ##STR00028## wherein R.sub.1 and R.sub.6
are each independently of the other H, CH.sub.3, CF.sub.3, F or Cl;
R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.7, R.sub.8, R.sub.9 and
R.sub.10 are each independently of all others H, halogen, R.sub.11,
COOH, COOR.sub.11, COO.sup.-, CONH.sub.2, CONHR.sub.11,
CONR.sub.11R.sub.12, CN, OH, OR.sub.11, OOCR.sub.11, OOCNH.sub.2,
OOCNHR.sub.11, OOCNR.sub.11R.sub.12, NO.sub.2, NH.sub.2,
NHR.sub.11, NR.sub.11R.sub.12, NHCOR.sub.12, NR.sub.11COR.sub.12,
N.dbd.CH.sub.2, N.dbd.CHR.sub.11, N.dbd.CR.sub.11R.sub.12, SH,
SR.sub.11, SOR.sub.11, SO.sub.2R.sub.11, SO.sub.3R.sub.11,
SO.sub.3H, SO.sub.3.sup.-, SO.sub.2NH.sub.2, SO.sub.2NHR.sub.11 or
SO.sub.2NR.sub.11R.sub.12; and R.sub.2 and R.sub.3, R.sub.3 and
R.sub.4, R.sub.4 and R.sub.5, R.sub.7 and R.sub.8, R.sub.8 and
R.sub.9, and/or R.sub.9 and R.sub.10 can also be linked together by
a direct bond or an O, S, NH or NR.sub.11 bridge; R.sub.11 and
R.sub.12 are each independently of the other C.sub.1-C.sub.12alkyl,
C.sub.1-C.sub.12cycloalkyl, C.sub.1-C.sub.12alkenyl,
C.sub.1-C.sub.12cycloalkenyl or C.sub.1-C.sub.12alkinyl, each of
which is uninterrupted or interrupted by oxygen, NH, NR.sub.13
and/or sulfur in two or more fragments each comprising at least 2 C
atoms, and each of which is also unsubstituted or substituted one
or more times with COOH, COOR.sub.13, COO.sup.-, CONH.sub.2,
CONHR.sub.13, CONR.sub.13R.sub.14, CN, oxo, OH, OR.sub.13,
OOCR.sub.13, OOCNH.sub.2, OOCNHR.sub.13, OOCNR.sub.13R.sub.14,
NR.sub.13, NH.sub.2, NHR.sub.13, NR.sub.13R.sub.14, NHCOR.sub.14,
NR.sub.13COR.sub.14, N.dbd.CH.sub.2, N.dbd.CHR.sub.13,
N.dbd.CR.sub.13R.sub.14, SH, SR.sub.13, SOR.sub.13,
SO.sub.2R.sub.13, SO.sub.3R.sub.13, SO.sub.3H, SO.sub.3.sup.-,
SO.sub.2NH.sub.2, SO.sub.2NHR.sub.13, SO.sub.2NR.sub.13R.sub.14or
halogen; or C.sub.7-C.sub.12aralkyl, C.sub.1-C.sub.11heteroaryl or
C.sub.6-C.sub.12aryl, each of which is unsubstituted or substituted
one or more times with COOH, COOR.sub.13, COO.sup.-, CONH.sub.2,
CONHR.sub.13, CONR.sub.13R.sub.14, CN, OH, OR.sub.13, OOCR.sub.13,
OOCNH.sub.2, OOCNHR.sub.13, OOCNR.sub.13R.sub.14, NO.sub.2,
NH.sub.2, NHR.sub.13, NR.sub.13R.sub.14, NHCOR.sub.14,
NR.sub.13COR.sub.14, N.dbd.CH.sub.2, N.dbd.CHR.sub.13,
N.dbd.CR.sub.13R.sub.14, SH, SR.sub.13, SOR.sub.13,
SO.sub.2R.sub.13, SO.sub.3R.sub.13, SO.sub.3H, SO.sub.3.sup.-,
SO.sub.2NH.sub.2, SO.sub.2NHR.sub.13, SO.sub.2NR.sub.13R.sub.14or
halogen; and each R.sub.13or R.sub.14is, independently of any other
R.sub.13 or R.sub.14, C.sub.1-C.sub.6alkyl, benzyl or phenyl, each
of which is unsubstituted or substituted one or more times with
substituents as defined above, with the proviso that the total
number of atoms in any substituent of R.sub.13 and R.sub.14 is from
1 to 8; whereby pairs of substituents selected from the group
consisting of all R.sub.13 and R.sub.14 can optionally be linked
together by a direct bond or an O, S, NH or NR.sub.11 bridge so as
to form rings, or a cis-trans isomer thereof or a salt of such
colorant or isomer having a salt-forming group, .beta.) a polymeric
dispersant comprising modified poly(meth)acrylate polymers
obtainable by the process comprising the steps a1) polymerizing in
a first step one or more ethylenically unsaturated monomers in the
presence of at least one nitroxylether having the structural
element of the formula ##STR00029## wherein X represents a group
having at least one carbon atom and is such that the free radical
X. derived from X is capable of initiating polymerization; or a2)
polymerizing in a first step one or more ethylenically unsaturated
monomers in the presence of at least one stable free nitroxyl
radical of the formula ##STR00030## and a free radical initiator;
wherein at least one monomer used in the steps a1) or a2) is a
C.sub.1-C.sub.6 alkyl or hydroxy C.sub.1-C.sub.6 alkyl ester of
acrylic or methacrylic acid; and a second step b) comprising the
modification of the polymer or copolymer prepared under a1) or a2)
by a transesterification reaction, an amidation, hydrolysis or
anhydride modification or a combination thereof, and .gamma.) a
solvent which is suitable for dispersions used in electrophoretic
displays.
2. A dispersion according to claim 1 wherein the colorant is a
pigment of the formula 1. ##STR00031##
3. A dispersion according to claim 1 wherein the colorant is a
sulfonic acid of the formula 2a ##STR00032## or a salt thereof
and/or a cis/trans-isomer of said acid or salt.
4. A dispersion according to claim 1 wherein the polymeric
dispersant is selected from modified poly(meth)acrylate polymers of
the formula II ##STR00033## wherein X represents oxygen or the
group NH, m is 0 or 10-20, p is 60-90, R.sub.15is hydrogen or
methyl, and R represents alkyl having up to 30 carbon atoms wherein
one or more carbon atoms may be replaced by oxygen and which is
unsubstituted or substituted by dimethylamino or trimethylamino
with the proviso that the group X--R is not the same in all (p)
moieties of the partial formula --CH.sub.2--C(R.sub.15)(CO--X--R)--
present in formula I, and salts of such polymers having a
salt-forming group.
5. A dispersion according to claim 1 wherein the solvent is
dodecane.
6. A dispersion according to claim 1 wherein the dispersed
particles have a diameter of 200-800 nm.
7. A bis-oxodihydro-indolylene-benzodifuranone colorant of the
formula 2a depicted in claim 3 or a salt thereof and/or a
cis/trans-isomer of said acid or salt.
8. (canceled)
9. A polymeric dispersant selected from modified poly(meth)acrylate
polymers of the formula II ##STR00034## wherein X represents oxygen
or the group NH, m is 0 or 10-20, p is 60-90, R.sub.15is hydrogen
or methyl, and R represents alkyl having up to 20 carbon atoms
wherein one or more carbon atoms may be replaced by oxygen and
which is unsubstituted or substituted by dimethylamino or
trimethylamino with the proviso that the group X--R is not the same
in all (p) moieties of the partial formula
--CH.sub.2--C(R.sub.15)(CO--X--R)-- present in formula I and the
different groups X--R are randomly distributed along the polymer
chain, or a salt of such dispersant having a salt-forming
group.
10. A dispersant according to claim 9 wherein in up to 20% of said
p moieties of the partial formula
--CH.sub.2--C(R.sub.15)(CO--X--R)-- R is unsubstituted
C.sub.1-6alkyl, while in the remaining moieties R is different from
unsubstituted C.sub.1-6alkyl.
11. An electrophoretic display comprising a dispersion of a
bis-oxodihydro-indolylene-benzodifuranone colorant of the formula I
and a polymeric dispersant as defined in claim 1 and a solvent
which is suitable for dispersions used in electrophoretic displays.
Description
[0001] The invention relates to a pigment dispersion, especially a
black pigment dispersion, comprising a
bis-oxodihydro-indolylene-benzodifuranone colourant, a specific
dispersant, and a suitable solvent, the use of said dispersion,
colourants and/or dispersants in electrophoretic displays, and to
novel bis-oxodihydro-indolylene-benzodifuranone colourants and
dispersants.
[0002] As discussed in U.S. Pat. No. 7,002,728 B2, the presently
preferred form of electrophoretic medium comprises white titania
and carbon black particles in a hydrocarbon suspending fluid, this
hydrocarbon being used alone or in admixture with a chlorinated
hydrocarbon or other low dielectric constant fluid. Most other
prior art electrophoretic displays which require a black pigment
have also used carbon black for this purpose, apparently largely
because the material is readily available in mass quantities and
very inexpensive. However, a number of problems with prior art
electrophoretic displays are associated with the use of carbon
black for the black electrophoretic particles. Carbon black has a
complex and poorly understood surface chemistry, which may vary
widely with the specific raw material (typically petroleum) and the
exact process used for the carbon black production. Carbon black
pigment particles also have a poorly understood aggregate, fractal
structure. Furthermore, carbon black is notoriously effective in
adsorbing gases and liquids with which it comes into contact, and
such adsorbed gases and liquids can change the physicochemical
properties of the carbon black surface. Hence, it is difficult to
ensure consistent surface properties of carbon black from batch to
batch. This is especially problematic in electrophoretic displays,
since the electrophoretic particles used are typically so small (of
the order of 1 .mu.m) that their properties are dominated by the
properties of their surfaces.
[0003] As also stated in U.S. Pat. No. 7,002,758 carbon black
presents certain peculiar difficulties in obtaining proper charging
of particles in opposite charge dual particle electrophoretic
displays. Specifically, it has been found that when using carbon
black and titania as the black and white particles respectively in
an opposite charge dual particle electrophoretic display,
combinations of charging agents and other materials which produce
all positively charged carbon black particles tend to produce a
minor proportion of titania particles which are also positively
charged. The resultant mixture of negatively and positively charged
titania particles leads to contamination of the extreme optical
states of the medium, thus adversely affecting its contrast
ratio.
[0004] Carbon black is also known to have electrical conductivity,
not only in bulk, but also dispersed in polymers, at least to an
extent to give antistatic properties (S. P. Rwei et al., Colloid.
Polym. Sci. 2002, 280, pages 1110-1115) and also in a dispersion in
mineral oils (J. Electroanal. Chem. 2005, 577, 67-78). This means
that an electric current will flow through the dispersion upon
application of an electric field, leading either to a break-down of
the field and, hence, the orientation of the particles (in case of
a field once applied without continuously keeping a certain
voltage) or requiring electrical energy to compensate for this.
[0005] There is thus a need for a black particle for use in
electrophoretic media that does not suffer from the problems
associated with the use of carbon black, e.g. for a dispersion of a
black particle, said dispersion having low electrical conductivity,
i.e. a high resistance. However, the search for such a black
particle is subject to considerable difficulties. Although the
optical properties of numerous pigments are of course known from
their use in the paint and similar industries, a pigment for use in
an electrophoretic display must possess several properties in
addition to appropriate optical properties. The pigment must be
compatible with the numerous other components of the
electrophoretic medium, including the suspending fluid, any other
pigment particles present, charge control agents and surfactants
typically present in the suspending fluid, and the capsule wall
material (if a capsule wall is present). The pigment particles must
also be able to sustain a charge when suspended in the suspending
fluid, and the zeta potentials of the particles caused by such
charges should all be of the same polarity and should not extend
over an excessively wide range, or the electrophoretic medium may
not have desirable electro-optic properties; for example, if some
particles have very low zeta potentials, a very long driving pulse
may be required to move such particles to a desired position within
the electrophoretic medium, resulting in slow switching of the
medium. It will be appreciated that such information relating to
the ability of pigment particles to acquire and hold charges is not
available for most pigments potentially usable in an
electrophoretic display, since such electrical properties are
irrelevant to the normal commercial uses of the pigments.
[0006] The same arguments are also valid, if the partner of the
black pigment is not a white, but a colored particle, and for this
display Yellow/Black, Red/Black, Green/Black and Blue/Black
particles systems are needed with the same characteristics as the
above-mentioned Black/White systems.
[0007] It has now surprisingly been found that a composition
comprising certain specific dispersants and certain
bis-oxodihydro-indolylene-benzodifuranone colourants, said
colourants being generically described in WO 00/24736 A1, or the
"violet powder" specifically described in Example 12b thereof can
be used as replacement for carbon black in electrophoretic
displays. Thus, in the presence of suitable additives (dispersants)
dispersions of a purely organic black pigment in media with low
conductivity and low permittivity can be prepared, which show
electrophoretic mobility under the influence of an electric field
and, hence, can be used as black pigment for electrophoretic
display applications, with lower conductivity and thus lower power
consumption than the state of the art.
DESCRIPTION OF THE DRAWING
[0008] FIG. 1 illustrates the three-point electrode geometry in one
particular well of a 96-well-plate (cf. Example 11 for more
information). The big spots represent the connection points for the
electrodes. The resistance is measured between the half-circle
electrodes, the center electrode serving for grounding.
[0009] The invention relates to a dispersion which is useful for
electrophoretic displays, especially a dispersion wherein the
dispersed particles have a diameter of 100 to 1000 nm (nanometers)
preferably 200-800 nm, most preferably 300-600 nm, comprising a) a
bis-oxodihydro-indolylene-benzodifuranone colourant of the formula
I
##STR00002##
wherein R.sub.1 and R.sub.6 are each independently of the other H,
CH.sub.3, CF.sub.3, F or Cl, preferably H or F, most preferably H;
R.sub.2, R.sub.3, R.sub.4, R.sub.5, R.sub.7, R.sub.8, R.sub.9 and
R.sub.10 are each independently of all others H, halogen, R.sub.11,
COOH, COOR.sub.11, COO.sup.-, CONH.sub.2, CONHR.sub.11,
CONR.sub.11R.sub.12, CN, OH, OR.sub.11, OOCR.sub.11, OOCNH.sub.2,
OOCNHR.sub.11, OOCNR.sub.11R.sub.12, NO.sub.2, NH.sub.2,
NHR.sub.11, NR.sub.11R.sub.12, NHCOR.sub.12, NR.sub.11COR.sub.12,
N.dbd.CH.sub.2, N.dbd.CHR.sub.11, N.dbd.CR.sub.11R.sub.12, SH,
SR.sub.11, SOR.sub.11, SO.sub.2R.sub.11, SO.sub.3R.sub.11,
SO.sub.3H, SO.sub.3.sup.-, SO.sub.2NH.sub.2, SO.sub.2NHR.sub.11 or
SO.sub.2NR.sub.11R.sub.12; and R.sub.2 and R.sub.3, R.sub.3 and
R.sub.4, R.sub.4 and R.sub.5, R.sub.7 and R.sub.8, R.sub.8 and
R.sub.9, and/or R.sub.9 and R.sub.10 can also be linked together by
a direct bond or an O, S, NH or NR.sub.11 bridge; R.sub.11 and
R.sub.12 are each independently of the other C.sub.1-C.sub.12alkyl,
C.sub.1-C.sub.12cycloalkyl, C.sub.1-C.sub.12alkenyl,
C.sub.1-C.sub.12cycloalkenyl or C.sub.1-C.sub.12alkinyl, each of
which is uninterrupted or interrupted by oxygen, NH, NR.sub.13
and/or sulfur in two or more fragments each comprising at least 2 C
atoms, and each of which is also unsubstituted or substituted one
or more times with COOH, COOR.sub.13, COO.sup.-, CONH.sub.2,
CONHR.sub.13, CONR.sub.13R.sub.14, CN, oxo, OH, OR.sub.13,
OOCR.sub.13, OOCNH.sub.2, OOCNHR.sub.13, OOCNR.sub.13R.sub.14,
NR.sub.13, NH.sub.2, NHR.sub.13, NR.sub.13R.sub.14, NHCOR.sub.14,
NR.sub.13COR.sub.14, N.dbd.CH.sub.2, N.dbd.CHR.sub.13,
N.dbd.CR.sub.13R.sub.14, SH, SR.sub.13, SOR.sub.13,
SO.sub.2R.sub.13, SO.sub.3R.sub.13, SO.sub.3H, SO.sub.3.sup.-,
SO.sub.2NH.sub.2, SO.sub.2NHR.sub.13, SO.sub.2NR.sub.13R.sub.14or
halogen; or C.sub.7-C.sub.12aralkyl, C.sub.1-C.sub.11heteroaryl or
C.sub.6-C.sub.12aryl, each of which is unsubstituted or substituted
one or more times with COOH, COOR.sub.13, COO.sup.-, CONH.sub.2,
CONHR.sub.13, CONR.sub.13R.sub.14, CN, OH, OR.sub.13, OOCR.sub.13,
OOCNH.sub.2, OOCNHR.sub.13, OOCNR.sub.13R.sub.14, NO.sub.2,
NH.sub.2, NHR.sub.13, NR.sub.13R.sub.14, NHCOR.sub.14,
NR.sub.13COR.sub.14, N.dbd.CH.sub.2, N.dbd.CHR.sub.13,
N.dbd.CR.sub.13R.sub.14, SH, SR.sub.13, SOR.sub.13,
SO.sub.2R.sub.13, SO.sub.3R.sub.13, SO.sub.3H, SO.sub.3.sup.-,
SO.sub.2NH.sub.2, SO.sub.2NHR.sub.13, SO.sub.2NR.sub.13R.sub.14or
halogen; and each R.sub.13or R.sub.14is, independently of any other
R.sub.13or R.sub.14, C.sub.1-C.sub.6alkyl, benzyl or phenyl, each
of which is unsubstituted or substituted one or more times with
substituents as defined above, with the proviso that the total
number of atoms in any substituent of R.sub.13 and R.sub.14 is from
1 to 8; whereby pairs of substituents selected from the group
consisting of all R.sub.13 and R.sub.14 can optionally be linked
together by a direct bond or an O, S, NH or NR.sub.11 bridge so as
to form rings, or a cis-trans isomer thereof or a salt of such
colourant or isomer having a salt-forming group, .beta.) a
polymeric dispersant comprising modified poly(meth)acrylate
polymers obtainable by the process comprising the steps a1)
polymerizing in a first step one or more ethylenically unsaturated
monomers in the presence of at least one nitroxylether having the
structural element of the formula
##STR00003##
wherein X represents a group having at least one carbon atom and is
such that the free radical X. derived from X is capable of
initiating polymerization; or a2) polymerizing in a first step one
or more ethylenically unsaturated monomers in the presence of at
least one stable free nitroxyl radical of the formula
##STR00004##
and a free radical initiator; wherein at least one monomer used in
the steps a1) or a2) is a C.sub.1-C.sub.6 alkyl or hydroxy
C.sub.1-C.sub.6 alkyl ester of acrylic or methacrylic acid; and a
second step b) comprising the modification of the polymer or
copolymer prepared under a1) or a2) by a transesterification
reaction, an amidation, hydrolysis or anhydride modification or a
combination thereof, and .gamma.) a solvent which is suitable for
dispersions used in electrophoretic displays.
[0010] In the following the components of the dispersion are
described in more detail.
Bis-Oxodihydro-Indolylene-Benzodifuranone Colourants.
[0011] Said cis-trans isomers of the colourant of formula I have
the following core structures (omitting the substituents), the
trans-trans isomer of the above formula I probably being the most
stable, the cis-cis isomer probably being the least stable of said
isomers.
##STR00005##
[0012] When the compound of formula (I) is anionic, its charge may
be compensated by any known suitable cation, for example a
metallic, organic, inorganic or metal organic cation, such as
preferably an alkali, earth alkali or transition metal, ammonium,
primary ammonium, secondary ammonium, ternary ammonium, e.g.
trialkylammonium, quaternary ammonium, e.g. tetraalkylammonium, or
an organic metal complex.
[0013] The colourants of formula (I) are both reflective and
transparent to near infra-red radiation, thus limiting heat
buildup, however the ratio of reflectance and transmittance depends
on their particle size. The reflectance (including diffracted
reflectance) is much more significant with large particles, such as
those having a thickness of .gtoreq.0.4 .mu.m, while transmittance
is preponderant in the case of tiny particles, such as those having
a size of from 0.01 to 0.3 .mu.m, as well as in the case of dyes
which dissolve into the substrate.
[0014] The instant colourants of formula (I) are normally obtained
from the synthesis in the form of very large agglomerates and
aggregates of unattractive dark colours and are highly difficult to
disperse, such as the violet powder obtained according to example
12b of WO00/24736. However, it has been found that these crude
powders can easily be transformed into suitable colourants just by
wet-milling them with milling aids in the presence of a solvent,
preferably an alcohol, amide, ester, ether or ketone, thus
obtaining particles of mean size.ltoreq.0.5 .mu.m, preferably from
0.01 to 0.3 .mu.m, which show surprisingly very attractive black
hues similar to carbon black. Wet-milling can for example be
performed in an attritor, such as a Dyno.RTM. or Netzsch.RTM. mill,
Skandex.RTM. paint shaker or the like, for example using glass or
ceramics (e.g. zirconia) pearls of size preferably from 0.1 to 3.0
mm, in particular from 0.5 to 1.0 mm. The amount of alcohol, amide,
ester, ether or ketone is adequately from 0.1 to 1000 parts per
part of colourant, preferably from 1 to 10 parts per part of
colourant. Adequate solvents for wet-milling and/or
recrystallisation are well-known in the art. The solvents disclosed
for example in EP0774494, EP0934364 and WO02/068541 are
specifically incorporated herein by reference.
[0015] The substituents in formula I and the general terms used in
defining them have the following preferred meanings:
R.sub.2, R.sub.4, R.sub.5, R.sub.7, R.sub.9, and R.sub.10 are
preferably H, F or Cl, especially H. R.sub.3 and R.sub.8 are
preferably H, NO.sub.2, OCH.sub.3, OC.sub.2H.sub.5, Br, Cl,
CH.sub.3, C.sub.2H.sub.5, N(CH.sub.3).sub.2,
N(CH.sub.3)(C.sub.2H.sub.5), N(C.sub.2H.sub.5).sub.2,
.alpha.-naphthyl, .beta.-naphthyl or SO.sub.3.sup.-. Preferably,
R.sub.1is identical to R.sub.6, R.sub.2is identical to R.sub.7,
R.sub.3is identical to R.sub.8, R.sub.4is identical to R.sub.9,
and/or R.sub.5is identical to R.sub.10. C.sub.1-C.sub.12Alkyl is,
for example, methyl, ethyl, n-propyl, isopropyl, n-butyl,
sec-butyl, isobutyl, tert-butyl, 2-methyl-butyl, n-pentyl,
2-pentyl, 3-pentyl, 2,2-dimethylpropyl, n-hexyl, heptyl, n-octyl,
1,1,3,3-tetramethylbutyl, 2-ethylhexyl, nonyl, decyl, undecyl or
dodecyl. C.sub.3-C.sub.12Cycloalkyl is, for example, cyclopropyl,
cyclopropyl-methyl, cyclobutyl, cyclopentyl, cyclohexyl,
cyclohexyl-methyl, trimethylcyclohexyl, thujyl, norbornyl, bornyl,
norcaryl, caryl, menthyl, norpinyl, pinyl, 1-adamantyl or
2-adamantyl. C.sub.2-C.sub.12Alkenyl is, for example, vinyl, allyl,
2-propen-2-yl, 2-buten-1-yl, 3-buten-1-yl, 1,3-butadien-2-yl,
2-penten-1-yl, 3-penten-2-yl, 2-methyl-1-buten-3-yl,
2-methyl-3-buten-2-yl, 3-methyl-2-buten-1-yl, 1,4-pentadien-3-yl,
or any desired isomer of hexenyl, octenyl, nonenyl, decenyl or
dodecenyl. C.sub.3-C.sub.12Cycloalkenyl is, for example,
2-cyclobuten-1-yl, 2-cyclopenten-1-yl, 2-cyclohexen-1-yl,
3-cyclohexen-1-yl, 2,4-cyclohexadien-1-yl, 1-p-menthen-8-yl,
4(10)-thujen-10-yl, 2-norbornen-1-yl, 2,5-norbornadien-1-yl,
7,7-dimethyl-2,4-norcaradien-3-yl or camphenyl.
C.sub.2-C.sub.12Alkinyl is, for example, 1-propin-3-yl,
1-butin-4-yl, 1-pentin-5-yl, 2-methyl-3-butin-2-yl,
1,4-pentadiin-3-yl, 1,3-pentadiin-5-yl, 1-hexin-6-yl,
cis-3-methyl-2-penten-4-in-1-yl, trans-3-methyl-2-penten-4-in-1-yl,
1,3-hexadiin-5-yl, 1-octin-8-yl, 1-nonin-9-yl, 1-decin-10-yl or
1-dodecin-12-yl. C.sub.7-C.sub.12Aralkyl is, for example, benzyl,
2-benzyl-2-propyl, 6-phenyl-ethyl, 9-fluorenyl,
.alpha.,.alpha.-dimethylbenzyl, .omega.-phenyl-butyl,
.omega.-phenyl-pentyl or .omega.-phenyl-hexyl. When
C.sub.7-C.sub.12aralkyl is substituted, either the alkyl moiety or
the aryl moiety of the aralkyl group can be substituted.
C.sub.6-C.sub.12Aryl is, for example, phenyl, naphthyl or
1-biphenyl. Halogen is for example F, Cl, Br or J, preferably F on
alkyl and Cl or Br on aryl. C.sub.1-C.sub.11Heteroaryl is an
unsaturated or aromatic radical having 4n+2 conjugated
.pi.-electrons, for example 2-thienyl, 2-furyl, 1-pyrazolyl,
2-pyridyl, 2-thiazolyl, 2-oxazolyl, 2-imidazolyl, isothiazolyl,
triazolyl, tetrazolyl or any other ring system consisting of
thiophene, furan, thiazole, oxazole, imidazole, isothiazole,
thiadiazole, triazole, pyridine, pyrazine, pyrimidine, pyridazine
and benzene rings and unsubstituted or substituted by from 1 to 6
ethyl substituents.
[0016] Heterocyclic groups are for example
##STR00006##
[0017] Heterocyclic groups may also be formed by linking adjacent
substituents of aryl, for example
##STR00007##
[0018] Preferred colourants are the pigment of the formula 1
##STR00008##
and the novel sulfonic acid of the formula 2a
##STR00009##
or a salt thereof and/or a cis/trans-isomer of said acid or
salt.
[0019] The invention relates also to said novel novel sulfonic acid
of the formula 2a or a salt thereof and/or a cis/trans-isomer of
said acid or salt.
[0020] The bis-oxodihydroindolylen-benzodifuranone colourants of
the present invention are prepared e.g. as described in WO00/24736
A1, especially according or in analogy to the method disclosed in
example 12b of WO00/24736 A1. Novel colourants of the formula I
described in the present patent application carrying a sulfonic
acid group or isomers or tautomers thereof can be also prepared by
reaction of the compound disclosed in example 12b of WO00/24736 A1
with fuming sulfuric acid.
Specific Dispersants
[0021] Said specific dispersants are polymers or copolymers,
preferably modified polyacrylate or polymethacrylate polymers,
especially block copolymers comprising modified polyacrylate or
polymethacrylate polymers, obtainable by the process described in
WO 2006/074969 A1 (which is incorporated herein by reference)
comprising the steps
a1) polymerizing in a first step one or more ethylenically
unsaturated monomers in the presence of at least one nitroxylether
having the structural element of the formula
##STR00010##
wherein X represents a group having at least one carbon atom and is
such that the free radical X. derived from X is capable of
initiating polymerization; or a2) polymerizing in a first step one
or more ethylenically unsaturated monomers in the presence of at
least one stable free nitroxyl radical of the formula
##STR00011##
and a free radical initiator; wherein at least one monomer used in
the steps a1) or a2) is a C.sub.1-C.sub.6 alkyl or hydroxy
C.sub.1-C.sub.6 alkyl ester of acrylic or methacrylic acid; and a
second step b) comprising the modification of the polymer or
copolymer prepared under a1) or a2) by a transesterification
reaction, an amidation, hydrolysis or anhydride modification or a
combination thereof.
[0022] For the reasons stated on pages 2 and 3 of WO 2006/074969 A1
the dispersants obtainable by the above process (which employs a
post-polymerisation modification technique) differ distinctly in
structural respect from polymers with same monomer composition, but
synthesized directly from corresponding monomers without
post-modification. It should especially be noted that the monomer
distribution which results from the transesterification step, is
only governed by the transesterification reaction and can be
expected to provide a more uniform i.e. random distribution along
the polymer chain, as compared to direct synthesis by radical
polymerisation.
[0023] The ethylenically unsaturated monomer in step a1 or a2 is
preferably selected from isoprene, 1,3-butadiene,
.alpha.-C.sub.5-C.sub.18alkene, 4-vinyl-pyridine or pyridinium-ion,
2-vinyl-pyridine or pyridinium-ion, vinyl-imidazole or
imidazolinium-ion, dimethylacrylamide,
3-dimethylamino-propylmethacrylamide, styrene, .alpha.-methyl
styrene, p-methyl styrene, p-tert-butyl-styrene or a compound of
formula CH.sub.2.dbd.C(R.sub.a)--(C.dbd.Z)--R.sub.b, wherein
R.sub.ais hydrogen or methyl, R.sub.bis NH.sub.2, O.sup.-
(Me.sup.+), unsubstituted C.sub.1-C.sub.18alkoxy,
C.sub.2-C.sub.100alkoxy interrupted by at least one N and/or O
atom, or hydroxy-substituted C.sub.1-C.sub.18alkoxy, unsubstituted
C.sub.1-C.sub.18alkylamino, di(C.sub.1-C.sub.18alkyl)-amino,
hydroxy-substituted C.sub.1-C.sub.18alkylamino or
hydroxy-substituted di(C.sub.1-C.sub.18alkyl)amino,
--O--CH.sub.2--CH.sub.2--N(CH.sub.3).sub.2or
--O--CH.sub.2--CH.sub.2--N.sup.+H(CH.sub.3).sub.2An.sup.-;
An.sup.- is a anion of a monovalent organic or inorganic acid; Me
is a monovalent metal atom or the ammonium ion; Z is oxygen or
sulfur; with the proviso that, as stated above, at least one
monomer used in the steps a1) or a2) is a C.sub.1-C.sub.6 alkyl or
hydroxy C.sub.1-C.sub.6 alkyl ester of acrylic or methacrylic
acid.
[0024] A nitroxylether having the structural element of the
formula
##STR00012##
[0025] is e.g. a compound of the formula
##STR00013##
[0026] Stable free radicals having a structural element
##STR00014##
are for example disclosed in EP-A-621 878 (Xerox).
[0027] Examples, such as
##STR00015##
are given in WO96/24620 (Atochem).
[0028] Particularly suitable nitroxylethers and nitroxyl radicals
are those of formulae
##STR00016## ##STR00017##
[0029] When the process according to route a2) is chosen, the free
radical initiator is preferably an azo compound (e.g.
2,2'-azobisisobutyronitrile), a peroxide (e.g. acetyl cyclohexane
sulphonyl peroxide), perester (e.g. disuccinic acid peroxide) or a
hydroperoxide (e.g. t-butyl hydroperoxide).
[0030] Preferably the first polymerization step is carried out
according to the polymerization reactions a1).
[0031] Preferably the second step b) is a transesterification
reaction, hydrolysis or an anhydride modification. Particularly
preferred is a transesterification reaction.
[0032] The transesterification preferably comprises the removal of
the C.sub.1-C.sub.6 alcohol byproduct by distillation.
[0033] In a specific embodiment step a1 or a2 of the above
described process is carried out twice and a block copolymer is
obtained wherein in the first or second radical polymerization step
the monomer or monomer mixture contains 50 to 100% by weight, based
on total monomers, of a C.sub.1-C.sub.6 alkyl or hydroxyalkyl ester
of acrylic or methacrylic acid and in the second or first radical
polymerization step respectively, the ethylenically unsaturated
monomer contains no primary or secondary ester bond.
[0034] When a block copolymer is prepared it is preferred that in
the first polymerization step the monomer or monomer mixture
contains from 50 to 100% by weight based on total monomers of a
C.sub.1-C.sub.6 alkyl or hydroxyalkyl ester of acrylic or
methacrylic acid and in the second polymerization step the
ethylenically unsaturated monomer is 4-vinyl-pyridine or
pyridinium-ion, 2-vinyl-pyridine or pyridinium-ion, vinyl-imidazole
or imidazolinium-ion, dimethylacrylamide,
3-dimethylaminopropylmethacrylamide, styrene, .alpha.-methyl
styrene, p-methyl styrene or p-tert-butyl-styrene.
[0035] In a specific embodiment of the invention the block
copolymer is a gradient block copolymer.
[0036] As mentioned above it is mandatory that the polymer or
copolymer is prepared by controlled free radical polymerization
(CFRP). Solomon et al. in U.S. Pat. No. 4,581,429 have firstly
described such processes using stable free nitroxyl radicals as
controlling agents. These are the steps defined under a1) and a2)
above.
[0037] U.S. Pat. No. 4,581,429 discloses a free radical
polymerization process by controlled or "living" growth of polymer
chains, which produces defined oligomeric homopolymers and
copolymers, including block and graft copolymers. Disclosed is the
use of initiators of the partial formula R'R''N--O--X. In the
polymerization process the free radical species R'R''N--O. and .X
are generated. .X is a free radical group, e.g. a tert.-butyl or
cyanoisopropyl radical, capable of polymerizing monomer units
containing ethylene groups.
[0038] As stated above, reaction step b) comprises the modification
of the polymer or copolymer prepared by reaction steps a1) or a2)
by a transesterification reaction, an amidation, hydrolysis or
anhydride modification or a combination thereof.
[0039] Transesterification means to replace the alcohol radical in
an ester group of the polymer or copolymer by another alcohol
radical. Preferably the alcohol radical to be replaced is methanol,
ethanol, propanol or butanol. Typically the transesterification
reaction is carried out at elevated temperatures, typically
70-200.degree. C., by reacting the CFRP polymer with the
corresponding alcohol using well-known catalysts, such as
tetra-isopropyltitanate, tetra-butyltitanate, or alkali- or earth
alkali alcoholates, like NaOMe, LiOMe or LiOC(CH.sub.3).sub.3.
Typically the low boiling product alcohol is removed from the
transterification reaction mixture by distillation. If needed,
catalyst residues may be removed by adsorption or extraction or
otherwise processed or inactivated by known methods, like
hydrolysis with water or acids. The choice of the replacing alcohol
is important. The replacing alcohol controls the properties of the
resulting copolymer.
[0040] Hydrolysis means the cleavage of an ester bond under
alkaline or acidic conditions and can be carried out when the
polymer or copolymer contains ester functionalities. The degree of
hydrolysis may vary in a wide range and depends on reaction time
and conditions. For example 5 to 100%, preferably 10% to 70% of the
ester functionalities may be hydrolized, to form the free acid
group, from which also a salt can be prepared. The metal ion is
preferably an alkali metal ion, such as Li.sup.+, Na.sup.+ or
Ka.sup.+ or an ammonium cation, such as NH.sub.4.sup.+ or
NR.sub.4.sup.+, wherein R is hydrogen or C.sub.1-C.sub.18alkyl with
the proviso that the four R need not all have the same meaning.
[0041] Anhydride modification can be carried out when the polymer
or copolymer contains hydroxyl functionalities. The hydroxyl
functionalities come for example from hydroxyl functional monomers,
such as hydroxyethyl acrylate or methacrylate. Virtually all
aliphatic or aromatic anhydrides can be used in the modification
process. Examples for anhydrides are maleic acid anhydride,
pyromelitic acid anhydride, cyclohexyldiacid anhydride, succinic
acid anhydride, camphoric acid anhydride.
[0042] Preferably, the dispersants are polymeric dispersants
selected from modified poly(meth)acrylate polymers of the formula
II
##STR00018##
wherein X represents oxygen or the group NH, m is 0 or 10-20, p is
60-90, R.sub.15is hydrogen or methyl, and R represents alkyl having
up to 30, preferably up to 20, more preferably up to 16 carbon
atoms wherein one or more carbon atoms may be replaced by oxygen
and which is unsubstituted or substituted by dimethylamino or
trimethylamino with the proviso that the group X--R is not the same
in all (p) moieties of the partial formula
--CH.sub.2--C(R.sub.15)(CO--X--R)-- present in formula I and the
different groups X--R are randomly distributed along the polymer
chain, and salts of such polymers having a salt-forming group.
[0043] When m is 0 the pyridyl-ethylene moiety is absent.
[0044] Alkyl R having up to 30 carbon atoms wherein one or more
carbon atoms are replaced by oxygen and which is substituted by
dimethylamino or trimethylamino is e.g. 5-dimethylamino-3-oxapentyl
of the formula
(CH.sub.3).sub.2N--CH.sub.2--CH.sub.2--O--CH.sub.2--CH.sub.2-- or
5-trimethylamonio-3-oxapentyl, and is preferably different from
2-dimethylaminoethyl.
[0045] Preferably, alkyl R has 2-20, especially 4-16 carbon atoms
and is e.g. n-butyl or linear or branched C.sub.12-16alkyl, like
1-hexadecyl.
[0046] As stated above the group X--R must not be the same in all
(p) moieties of the partial formula
--CH.sub.2--C(R.sub.15)(CO--X--R)-- present in formula I.
Preferably, in up to 20% of said moieties R is unsubstituted
C.sub.1-6alkyl, e.g. 1-butyl, while in the remaining moieties R is
different from unsubstituted C.sub.1-6alkyl, e.g. linear or
branched C.sub.12-16alkyl, like 1-hexadecyl, or
5-dimethyl-amino-3-oxapentyl of the formula
(CH.sub.3).sub.2N--CH.sub.2--CH.sub.2--O--CH.sub.2--CH.sub.2-- or
5-trimethylamonio-3-oxapentyl.
[0047] A salt-forming group in a compound of the formula I is
especially a dimethylamino group which may be reacted e.g. with
methyliodide to form a trimethylamonio group. Suitable counterions
are e.g. tetraphenyl-borate or a dialkylphosphonate, like
didodecylphosphonate.
Solvents for the Dispersions
[0048] Examples of suitable solvents for dispersants are aliphatic
hydrocarbons, e.g. the high-purity isoparaffinic solvents with
narrow boiling ranges Isopar.TM. G and Isopar.TM. M; halogenated
hydrocarbons, like tetrachloroethylene and Halocarbon.TM. 0.8 (a
low molecular weight polymer of chlorotrifluoroethylene), and
silicone fluids. A preferred dispersant is dodecane.
[0049] The dispersions of the present invention can be used in
electrophoretic displays.
[0050] The invention relates also to the use in an electrophoretic
display of a bis-oxodihydro-indolylene-benzodifuranone colourant of
the formula I, and/or of a polymeric dispersant as defined herein,
and to the use in an electrophoretic display of a dispersion
comprising a bis-oxodihydro-indolylene-benzodifuranone colourant of
the formula I, a polymeric dispersant as defined herein, and a
suitable solvent.
[0051] The invention relates also to an electrophoretic display
comprising a dispersion of a
bis-oxodihydro-indolylene-benzodifuranone colourant of the formula
I, a polymeric dispersant as defined herein and a solvent which is
suitable for dispersions used in electrophoretic displays.
[0052] The following Examples illustrate the invention.
EXAMPLES
Abbreviations
[0053] DMAPMA: N,N-Dimethylaminopropyl methacrylamide
DMAEE: Dimethylaminoethoxyethanol
[0054] hyflo: Hyflo SuperCel.RTM. (Fisher Scientific, Inc.); flux
calcined diatomaceous earth GPC: gel permeation chromatography
LDI-TOF MS: Laser desorption/ionization time-of-flight mass
spectrometry M.sub.n: Number average molecular weight nBA:
n-butylacrylate PDI: Polydispersity (The polydispersity of a sample
is defined as weight average molecular weight M.sub.w divided by
M.sub.n and gives an indication just how narrow a distribution is.)
Ph.sub.4BNa: Tetraphenylborane sodium salt THF: tetrahydrofurane
4VP: 4-vinyl-pyridine
Abbreviations for NMR Spectra
[0055] s: singulet t: triplet m: multiplet
Reagents:
[0056] Cetylalcohol (98% purel-hexadecanol; obtainable from the
company Cognis) LIAL.RTM. 125 A: mixture of straight chain and
mono-branched C.sub.12-15 alkanols from Sasol Olefins and
Surfactants GmbH. Lupragen.RTM. N 107: Dimethylaminoethoxyethanol
(obtainable from the company BASF)
General Remarks on the Nomenclature and Formulae Given Herein for
Polymeric Dispersants
[0057] As stated in Example 6 the transesterification proceeds at
random. This is not reflected properly by many formulae, like
formula 4 according to which it would seem that there is a block of
butyl esters and a block of C.sub.12-15-alkyl esters. Nevertheless,
said formulae are more illustrative than e.g. formula 4' and have
been used for this reason. In contrast to the formulae, the
abbreviated names better reflect which part of the polymer is
random and which part is a block. For example the name
poly(nBA-co-LialA-b-DMAPMA) given in Example 7 describes a polymer
comprising a block (characterized by the letter "b") of
poly-n-butylacrylate wherein the butyl group has at random be
replaced by LIAL.RTM. alcohols, i.e. poly(nBA-coLialA) and another
block of poly-dimethylaminopropylmethacrylamide. The approximated
numbers of the monomers in said blocks are given e.g. in Example 7
as (11-co-60)-b-10, i.e. there are approximately 11 n-butylacrylate
units at random copolymerized with 60 Lial-acrylate units followed
by a block of 10 dimethylaminopropylmethacrylamide (DMAPMA) units.
It should, however, be noted that the abbreviated names do not
mention the end groups on both sides of the polymer, i.e. e.g. the
1-phenyl-ethyl group.
Preparation of Known and Novel Pigments
Example 1
Manufacture of the Pigment of the Formula 1
##STR00019##
[0059] The synthesis of the pigment of the above formula 1 from
bisbenzofuranone and isatin is described in Example 12b on page 35
of WO 00/24736 A1). The product is described in WO 00/24736 A1 as a
"violet powder". While the inventors of the present patent
application consider the above formula 1 to represent the most
likely structure of the product obtained according to said Example
12b, the structure is not absolutely certain. The correct structure
could also correspond to an isomer, especially a cis/trans-isomer
of formula 1, or to a mixture of such isomers.
[0060] A new synthesis which yields an improved form of the pigment
of the above formula 1, a cis/trans-isomer thereof or a mixture of
such isomers is described hereinafter:
[0061] A mixture of 8.5 g of 2,5-dihydroxy-1,4-benzenediacetic acid
(0.37 Mol, Aldrich), 11 g Isatin (0.74 Mol, Aldrich 98%) and 14 g
of p-toluenesulfonic acid-monohydrate (Fluka purum) in 800 ml of
glacial acetic acid is stirred during 14 hour at 105.degree. C. The
reaction mixture is cooled to room temperature and the suspension
filtered over a paper filter, washed with 250 ml of acetic acid,
200 ml of methanol and 500 ml of water. The black powder is dried
in a vacuum oven at 70.degree. C./104 Pa.
Examples 2 to 5
General Procedure for Examples 2 to 5
##STR00020##
[0063] 5.00 g of the black pigment of the above formula 1 or an
isomer thereof (obtained by the new synthesis described in Example
1) are dissolved under stirring in 30 ml of fuming sulfuric acid
(comprising 25% of free SO.sub.3). The dark violet solution, whose
temperature has reached 30.degree. C., is cooled down to 20.degree.
C., stirred for 4 hours, discharged into 500 ml of an
ice/water-mixture and stirred for another hour. 25 g (i.e. a
multiple stoichiometric excess) of the amine or ammonium salt
specified in Examples 2 to 5 are added within 5 minutes. The black
suspension is stirred for 30 minutes, filtered and washed with 50
ml of water. The humid presscake is suspended in 100 ml of water, 5
g of the amine or ammonium salt are added, and the product is
extracted twice each with 150 ml of methylene chloride. The two
organic phases are merged and stirred into 1200 ml of hexane; the
product precipitates as small crystals. The suspension is stirred
for 30 minutes and filtered on a fibre glass filter. As the product
tends to liquefy on the filter, the product is dissolved off the
filter with 100 ml of methylene chloride and isolated by
evaporating the solvent on the rotavapor at slightly elevated
temperature under vacuum.
[0064] The products contain predominantly two sulfo groups, as
determined by MS technique. Based on .sup.1H-NMR-data the exact
location of the sulfo groups is uncertain.
Example 2a
Manufacture of the Pigment of the Formula 2a
[0065] In order to manufacture a disulfonic acid of the formula 2
where the location of the sulfo groups is certain, i.e. as depicted
in the below formula 2a, the following process of manufacture is
used:
[0066] A mixture of 2.3 g of 2,5-dihydroxy-1,4-benzenediacetic acid
(0.01 Mol, Aldrich), 5.7 g isatin-5-sulfonic acid sodium salt
dihydrate (0.02 Mol, Fluka 98%) and 0.7 g p-toluenesulfonic
acid-monohydrat (Fluka purum) in 80 ml acetic acid and 20 ml water
is stirred during 14 hour at 105.degree. C. The reaction mixture is
cooled to 80.degree. C. and the suspension filtered over a paper
filter, washed with 80 ml of acetic acid and 100 ml of methanol.
The black powder is dried in a vacuum oven at 70.degree.
C./10.sup.4Pa (Pa=Pascal) yielding the compound of formula 2a;
LDI-TOF: m/z=608.
##STR00021##
Example 2
[0067] Tributylammonium salt of the above formula 2; used amine:
tributylamine. Yield: 2.1 g
Example 3
[0068] Trioctylmethylammonium salt of the above formula 2; used
ammonium salt: trioctylmethylammonium bromide. Yield: 1.6 g
[0069] The product is characterized by elemental analysis,
corresponding to the bis(trioctylmethylammonium) salt:
[0070] Found (Calculated): C 66.35% (67.92%); H 9.02% (8.85%); N
3.86% (4.17%); O 14.25% (14.29%); S 5.44% (4.77%). No residual
bromide is detected.
Example 4
[0071] Octadecyltrimethylammonium salt of the above formula 2; used
ammonium salt: octadecyltrimethylammonium bromide. Yield: 8.3 g
[0072] The product is characterized by elemental analysis,
corresponding to the mono(octadecyltrimethylammonium) salt
monohydrate:
[0073] Found (Calculated): C 59.06% (60.18%); H 7.46% (6.34%); N
4.01% (4.48%); O 21.25% (22.17%); S 6.78% (6.84%). No residual
bromide is detected.
Example 5
[0074] Tetraethylammonium salt of the above formula 2; used
ammonium salt: tetraethylammonium bromide. Yield: 1.2 g
Preparation of Reagents and Copolymers Used as Dispersants
Example 6
Synthesis of Compound 4 (4'), i.e. poly(nBA-co-CetylA-b-4VP)
##STR00022##
[0076] In a 500 mL flask equipped with a mechanical stirrer and a
distillation column with dry ice acetone cooling, 100.0 g of
poly(nBA-b-4VP), i.e. a block copolymer of n-butylacrylate and
4-vinylpyridine, degree of polymerization 75-b-15, described in
example A2 on page 36 of WO2006/074969 A1, 100 g of xylene and 71.7
g of cetylalcohol (molecular weight 242.5 g/mol; 45 mol % relative
to the n-butyl esters) are added and dried by azeotropic
distillation of the xylene. Three portions of 0.25 g of tert.
butoxylithium (LiO.sup.tBu) are added during 5 h at 190.degree. C.
The formed n-butanol is distilled off at reduced pressure. As a
result, 149.8 g of poly(nBA-co-CetylA-b-4VP) of the formula 4 are
obtained as a yellowish wax. Number average molecular weight
M.sub.n=15.400 g/mol (PDI 1.5). Analysis via gel permeation
chromatography (GPC) as well as .sup.1H-NMR indicate almost
quantitative conversion of the cetylalcohol.
[0077] The above formula 4 does probably not reflect the structure
of the obtained product correctly in that the transesterification
probably proceeds at random so that the true structure of the
obtained product seems to be better reflected by formula 4'.
Analogous comments apply to the below Examples 7 to 9.
Example 7
Synthesis of poly(nBA-co-LialA-b-DMAPMA) of Formula 6
##STR00023##
[0079] In a 350 ml flask equipped with a mechanic stirrer and a
distillation column with dry ice acetone cooling 90.5 g of the
copolymer of formula 5 and 100.3 g of Lial 125 (80 mol % relative
to the n-butyl esters) are placed and inertisized by bubbling
nitrogen through the solution during 1 hour at room temperature.
The mixture is heated to 135-142.degree. C. and catalyst is added
(4 portions of 350 mg of tetra(isopropyl)orthotitanate, each 2
hours). The formed n-butanol is distilled off at low pressure (200
mbar). After 8 hours the resulting brownish polymer is cooled to
room temperature, affording 145.1 g of the copolymer of the formula
6 (M.sub.n11300, PDI 1.35 (by GPC (THF)), solid content 97.3%
(halogen dryer 200.degree. C.) and a composition (according to
.sup.1H-NMR) for poly(nBA-co-LialA-b-DMAPMA) as
(11-co-60)-b-10.
[0080] The starting material of the formula 5 is obtained as
follows:
Step 7.1
[0081] In a 500 ml flask, equipped with a mechanic stirrer and
distillation column are loaded 122.5 g of poly-n-butylacrylate
[poly(nBA)] (synthesized analogous to Example A1 in WO2006/074969;
degree of polymerization 75 according to .sup.1H-NMR, M.sub.n=6830,
PDI=1.31 and 85.98 g of dimethylaminopropyl methacrylamide
(DMAPMA). The mixture is heated under nitrogen to 135.degree. C.
After 2.5 h the reaction is terminated by cooling below 100.degree.
C. and non-reacted monomer DMAPMA is distilled off at high vacuum
(<20 mbar) until a solid content of >98.0% is reached (by
halogen dryer 200.degree. C.).
[0082] As a result, 143 g of the brownish viscous block copolymer
of the formula 5 are isolated with M.sub.n[GPC (THF)] 7480, (PDI
1.32). According to analysis by .sup.1H-NMR the degree of
polymerization is determined for p(nBA-b-DMAPMA) as 71-b-10.
Example 8
Synthesis of the Copolymeric Salt of the Formula 7
[poly(nBa-co-LialA-co-DMAEE[Me-quat]A-b-DMAPMA)].sup.+(TPB).sup.-
##STR00024##
[0084] In a 500 mL flask equipped with a mechanic stirrer and a
distillation column with dry ice acetone cooling 200.0 g of
poly(nBA-b-4VP) of the formula 3 depicted in Example 6 with a
degree of polymerization of 75-b-15, prepared according to example
A2 in WO2006/074969, 203.1 g of Lial 125 (ca. 100 mol % relative to
the n-butyl esters) and 4.6 g of Lupragen N 107 (MW 133.2, ca. 3
mol % relative to the n-butyl esters; dimethylaminoethoxyethanol
[DMAEE]) are added. One portion of 2.5 g of
tetra(isopropyl)orthotitanate is added and the mixture is stirred
under inert conditions and low pressure for 8 hours at 140.degree.
C., distilling off formed n-butanol. At the end of the process,
residual excess alcohols are removed under high vacuum (20 mbar)
until solid content of >95% (halogen dryer, 200.degree. C.) is
reached. This affords a brownish viscous polymer with the average
(.sup.1H-NMR) composition for p(nBA-co-DMAEEA-co-Lial125A)-b-p(4VP)
as (5-co-1-co-70)-b-15 and a M.sub.n(GPC/THF) of 17.500 (PDI 1.31).
50.0 g of this polymer are placed in a 250 ml three necked flask,
equipped with a mechanical stirrer, and 100 g of n-dodecane are
added. The mixture is slightly heated to 40.degree. C. to obtain a
homogenous solution. After cooling to room temperature, 0.29 g of
methyliodide (1.0 equiv relative to amino-groups) are added to the
polymer solution and subsequently stirred overnight at room
temperature. The resulting quaternized polymer solution is obtained
with a solid content of 32.1% (halogen dryer, 200.degree. C.) and a
M.sub.n(GPC/THF) of the polymer of 14.300 (PDI 1.29). In the final
step, 0.66 g of sodium tetraphenylborate (Ph.sub.4BNa), dissolved
in 13.2 g of dodecane, are slowly added to the polymer solution and
stirred for 3 hours at room temperature. The resulting slightly
turbid mixture is filtered over hyflo resulting in a yellowish
solution (solid content 31.3%) and a M.sub.nof 14.300 (PDI 1.24) of
the salt of the formula 7. The average (.sup.1H-NMR) composition of
the cation is determined for
p(nBA-co-DMAEE[Me-quat]A-co-Lial125A)-b-p(4VP).sup.+ as
(5-co-1-co-70)-b-15.
Example 9
Synthesis of the Dispersant of Formula 9
[poly(nBA-co-LialA-co-DMAEE[H]A)-b-DMAPMA].sup.+(DDDP).sup.-
##STR00025##
[0086] 50.0 g of the copolymer of formula 8 are homogenously
dissolved in 283 g of n-dodecane at 50.degree. C. The
didodecylphosphonate (DDDP, 0.64 g) of the formula 10 described in
step 9.2 is added and stirred for 2 hours at 80.degree. C. The
ammonium salt of the formula 9 is obtained as a clear brownish
solution in n-dodecane. GPC(THF) of the polymer gives a M.sub.nof
18.800 (PDI 1.30). The average (.sup.1H-NMR) composition of the
cation p(nBA-co-DMAEE[H]A-co-Lial125A)-b-p(4VP).sup.+ is determined
to be (7-co-1-co-66)-b-14.
[0087] The starting materials are prepared as follows:
Step 9.1: Synthesis of the Copolymer of the Formula 8
[0088] In a 500 mL flask equipped with a mechanic stirrer and a
distillation column with dry ice acetone cooling, 175 g of the
copolymer of the formula 8 are prepared according to the procedure
of Example 8: 103.7 g of a p(nBA)-b-p(4VP) block copolymer with an
average (.sup.1H-NMR) composition of 73 nBA and 14 4-vinylpyridine
units, 110.1 g of Lial 125 (ca. 100 mol % relative to
n-butylesters), 1.0 g of Lupragen N 107 (MW 133.2; 1.5 mol %
relative to the n-butyl esters) and 1.3 g of
tetra(isopropyl)orthotitanate are transesterified (18 hours at
140.degree. C. and 200 mbar) to a brownish viscous copolymer of the
formula 8 with the average (.sup.1H-NMR) composition for
p(nBA-co-DMAEEA-co-Lial125A)-b-p(4VP) of (7-co-1-co-66)-b-14 and a
M.sub.n(GPC/THF) of 15.900 (PDI 1.61).
Step 9.2; Synthesis of Didodecylphosphonate (DDDP) of the Formula
10
##STR00026##
[0090] In a 250 ml three necked flask, equipped with a magnetic
stirring bar, 10.6 g of sodium hypophosphite monohydrate (Fluka, MW
106) are dissolved in 10 ml of water and cooled to 15.degree. C. To
this solution 7.51 g of concentrated sulfuric acid (97%, 0.75
equivalents) are slowly introduced, resulting in a turbid viscous
reaction mass. 35.4 g of 1-dodecene (2.0 equivalents) are added at
room temperature, followed by a solution of 2.42 g of dibenzoyl
peroxide (Bnz-O--O-Bnz; Fluka; 50% in water) in 20 ml of
1,4-dioxane. The inhomogeneous mixture is heated to 80-85.degree.
C. and stirred for 2 hours, followed by another portion of 2.42 g
of dibenzoyl peroxide (Fluka, 50% in water) in 20 ml of 1,4-dioxane
and stirring for 2 hours at 85.degree. C. After cooling to room
temperature, 50 ml of toluene are added, heated to 60.degree. C.,
and cooled to room temperature. The two phase system is seperated
and the aquous phase is extracted two times with each 50 ml of
toluene. The combined organic phases are washed with water and a
nearly saturated aqueous sodium chloride solution (brine; 2 times
20 ml and 1 time 20 ml respectively). After filtration over hyflo,
the toluene is evaporated to dryness. The residual solid is
dissolved in hot hexane (60.degree. C., 200 ml) and left to cool
down for crystallization. Part of the crystals are filtered off,
the filter cake is washed with cold hexane, and dryed at 25.degree.
C. on a rotorvap. This affords 14.65 g (36% yield) of the compound
of the formula 10 as a white crystalline material; .sup.1H-NMR
(CDCl3, ppm): 9.8 (s, 1H, OH); 1.5-1.8 (m, 8H, 2
P--CH.sub.2--CH.sub.2--)), 1.2-1.5 (m, 36H, 18-CH.sub.2--), 0.9 (t,
6H, 2 CH.sub.3).
Example 10
Synthesis of poly(nBA-co-LialA-b-4VP) of the Formula 11
##STR00027##
[0092] In a 100 mL flask equipped with a mechanical stirrer,
distillation column with dry ice acetone cooling, 18.77 g of
poly(nBA-b-4VP), degree of polymerization 73-b-14, prepared
according to example A2 in WO2006/074969, and 20.63 g of Lial-125
(80 mol % relative to the n-butyl esters) are added and degassed at
65.degree. C. for 60 minutes at 50 mbar. Three portions of 0.29 g
of titanium-bis(acetylacetonate)-bis-isopropylate are added during
6 hours at 142.degree. C. The formed n-butanol is distilled off at
reduced pressure.
[0093] As a result, 28.94 g of the copolymer of the formula 11
[poly(nBA-co-LialA-b-4VP)] are obtained as a brownish viscous
substance; M.sub.n=18.760 g/mol (PDI 1.34). Analysis via GPC as
well as .sup.1H-NMR indicate almost quantitative conversion of the
Lial-125 alcohol.
Example 11
Preparation and Characterization of Dispersions
[0094] This example illustrates the preparation of the oil phase
containing various dispersed electrophoretic black pigment
particles. The physical characteristics of the obtained dispersions
are given in Table 1 below.
General Procedure for the Preparation of the Dispersions:
[0095] 1.00 g of the pigment substance is milled by a disperser DAS
200 (Lau GmbH) for 15 hours at 25.degree. C. into 9.0 g of dodecane
(749.0 kg/m.sup.3) (Aldrich D22, 110-4) in the presence of 0.75 g
of the dispersant mentioned in Table 1. In the case of the
two-colour electrophoretic dispersion of Example 11i the
above-mentioned 1.00 g of the pigment substance are replaced by 0.5
g of each of the pigments mentioned in Example 11i.
[0096] The dispersion is diluted with further dodecane from 10% to
2% by weight. 20 .mu.l of this dispersion are further diluted with
dodecane to 1 ml before measurements by dynamic light
scattering.
[0097] The size [diameter in nm] and the zeta potential (.xi.) [mV]
of the dispersed pigment particles are measured by dynamic light
scattering by means of a Malvern Zetasizer Nano Series apparatus
(Malvern Instruments Ltd., United Kingdom). The resulting particle
sizes are shown in the row "Size" of the below Table 1 in units of
nanometers, the (calculated) electrophoretic mobilities in the row
p in units of 10.sup.-8 m.sup.2/Vs at 40V (the electrophoretic
mobility is the coefficient of proportionality between particle
speed and electric field strength), and the zeta potential in the
row "Zeta (mV)".
[0098] The electrophoretic mobility .mu. [is calculated from the
Smoluchowski relation (.xi.=.mu..eta./.di-elect cons. where .mu. is
the mobility, .eta.=1.344 mPa*s is the viscosity of the medium at
25.degree. C. and .di-elect cons.=2.0 is the dielectric constant at
20.degree. C.).
Measurement of the Resistance R
[0099] The resistance R [.OMEGA.] given in Table 1 is measured as
follows:
[0100] A dispersion of carbon black (Base Carbon Black from the
Cabot Modified Carbon Black Toolkit; Cabot Corp.) in dodecane is
prepared as reference, using copolymer 4 (cf. Example 6) SP-10515
as dispersant, according to the above "General Procedure for the
Preparation of the Dispersions".
[0101] Pure dodecane, the dispersion of carbon black, and the
dispersion of pigments (all in a concentration of 2% by weight) are
applied in identical volumes into wells of a 96-well-plate from
Gatlik Ltd. (Basel, Switzerland; http://www.gatlik.com/) with a
three-point electrode geometry for low conductivity, as described
in WO 2005/105292 A1 (cf. FIG. 1 thereof). The plates are made of
polyimide with flat gold electrodes in a double half-circle
arrangement as illustrated in FIG. 1 of the present patent
application for one particular well. The wells have a diameter of 5
mm and a depth of 2 mm. Before the measurements, the plate is
cleansed with ethanol until the resistance between the electrodes
is more than 10.sup.13.OMEGA.. The resistance is measured between
the half-circle electrodes, the center electrode serving for
grounding. For each sample of dispersion, measurements in three
different wells are performed, and the highest and the lowest value
excluded.
TABLE-US-00001 TABLE 1 Pigment Dispersant .mu. [10.sup.-8 m.sup.2/
[formula [formula Size Vs Zeta Example no./Example] no./Example]
Conc.** [nm] at 40 V] [mV] R [.OMEGA.] 11a Carbon 4/6 150 149 -3.4
.times. 10.sup.-3 -3.96 3.53 .times. 10.sup.9 Black* 11b 2/4 4/6
100 551 -2.32 .times. 10.sup.-2 -27.1 5.71 .times. 10.sup.9 11c 2a
(free 6/7 75 314 -3.09 .times. 10.sup.-2 -36.1 1.09 .times.
10.sup.10 disulfonic acid)/2a 11d 2a (free 11/10 75 338 -3.71
.times. 10.sup.-2 -43.2 4.36 .times. 10.sup.10 disulfonic acid)/2a
11e 1/1 8/9.1 75 511 -1.32 .times. 10.sup.-2 -15.4 4.69 .times.
10.sup.9 11f 1/1 4/6 75 471 -1.99 .times. 10.sup.-2 -23.2 Not
measured 11g 1/1 9/9 75 435 -2.59 .times. 10.sup.-2 -30.2 Not
measured 11h 1/1 7/8 75 411 2.29 .times. 10.sup.-2 -26.6 Not
measured 11i 1/1 + 6/7 75 493 -1.95 .times. 10.sup.-2 -22.7 Not
Pigment measured Yellow 128*** *Base Carbon Black from the Cabot
Modified Carbon Black Toolkit; Cabot Corp. **The row "conc." gives
the percentage of weight of dispersant relative to the weight of
pigment. ***CROMOPHTAL Jet Yellow 8GT; Ciba, Inc.
[0102] The resistance of the well with pure dodecane is
>10.sup.13.OMEGA. (>10.sup.13Ohm).
[0103] As can be seen from Table 1, in all cases the absolute value
of the zeta potential and the resistance of the dispersions of the
black pigments which are matter of this patent application
(Examples 11b to 11e) is higher than that of the reference material
carbon black (Example 11a).
[0104] The significance of zeta potential is that its absolute
(i.e. positive or negative) value is related to the stability of
colloidal dispersions. The zeta potential indicates the degree of
repulsion between adjacent, similarly charged particles in a
dispersion. For molecules and particles that are small enough, like
the nano particles of the present invention, a high zeta potential
confers stability, i.e. the dispersion resists aggregation. When
the potential is low, attraction exceeds repulsion and the
dispersion will break and flocculate. So, colloids with high zeta
potential (negative or positive) are electrically stabilized while
colloids with low zeta potentials tend to coagulate or flocculate.
The other importance of the zeta potential is that the mobility of
a particle under influence of an electric field is proportional to
the zeta potential. The higher the (absolute) zeta potential, the
faster is the movement of the particles and the switching between
the two states.
[0105] A high resistance (resistivity) of the dispersion is desired
in order to reduce its electrical conductivity, to get lower power
consumption of the display, and to get an image stable for a longer
time by application of an electrical field kept by a capacitor
under powerless conditions, respectively.
* * * * *
References